/// - 实现Deref trait允许我们重载解引用
/// - let a: A = A::new(); //前提：A类型比u实现Deref trait
/// - let b = &a;
/// - let c = *b
fn main() {
    let x = 5;
    let y = &x;
    assert_eq!(x, 5);
    assert_eq!(*y, 5); // 这里的y是解引用

    let z = Box::new(x);
    assert_eq!(*z, x);
    println!("Hello, world!");
}
